Astrophys. J., 707, 921-935 (2009/December-3)
IRAS 16293: a "Magnetic" tale of two cores.
RAO R., GIRART J.M., MARRONE D.P., LAI S.-P. and SCHNEE S.
Abstract (from CDS):
We present polarization observations of the dust continuum emission from the young star-forming region IRAS 16293. These observations of IRAS 16293, which is a binary system, were conducted by the Submillimeter Array at an observing frequency of 341.5 GHz (λ ∼ 880 µm) and with high angular resolution (∼2''-3''). We find that the large-scale global direction of the field, which is perpendicular to the observed polarization, appears to be along the dust ridge where the emission peaks. On smaller scales we find that the field structure is significantly different for the two components of the binary. The first component, source A, shows a magnetic field structure that is "hourglass" shaped as predicted from theoretical models of low-mass star formation in the presence of strong magnetic fields. However, the other component, source B, shows a relatively ordered magnetic field with no evidence of any deformation. We have possibly detected a third younger outflow from source A as seen in the SiO emission, which is in addition to the two well-known powerful bipolar outflows in this kinematically active region. There is an observed decrease in polarization toward the center and this "polarization hole" is similar to decreases seen in other young star-forming regions. Our calculations show that in IRAS 16293 the magnetic energy is stronger than the turbulent energy but is approximately similar to the centrifugal energy. There is a considerable misalignment between the outflow direction and the magnetic field axis, and this is roughly in agreement with model predictions where the magnetic energy is comparable to the centrifugal energy. In conjunction with other observations of the kinematics as determined from the outflow energetics and chemical differentiation, we find that our results provide additional evidence to show that the two protostars appear to be in different stages during their evolution.
ISM: individual: IRAS 16293-2422 - ISM: magnetic fields - polarization - stars: formation - submillimeter - techniques: polarimetric
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